The invention relates to an adjusting device for a vehicle seat with a silent ratchet including a first ratchet portion having an inner lining which is defined by a rotating body and a second ratchet portion which is a) arranged so as to oppose the first ratchet portion and to be capable of rotating about an axis of the inner lining and b) which carries at least one clamping lever capable of pivoting about an axis of the clamping lever, the clamping lever having a clamping area located in the neighbourhood of the inner lining and an actuating device for the clamping lever being provided so that the clamping lever may be pivoted in a controlled manner between the normal clamping position in which the lever is frictionally engaged with the inner lining, a non rotatable connection of the two ratchet portions being provided thereby, and a release position, in which the clamping area is located at a distance from the inner lining.
The adjusting device of the type mentioned above is provided with two pairs of clamping levers which are arranged, axially staggered by 180 degrees, in the same radial plane. The clamping levers are designed as flat parts. One clamping lever of each pair locks in one rotating direction, the other locks in the other rotating direction. In order to guard them from axial motion, a groove is provided in the inner lining. In the normal clamping position the four clamping levers abut the bottom of said groove.
The clamping levers engage the inner lining at an angle of nearly 90 degrees when they are in the clamping position. In other words, a connecting line of an axis of the clamping lever intersects a tangent with the osculation point of said clamping lever on the inner lining at the osculation point at an angle of approximately 90xc2x0.
Thus, the clamping forces substantially act radially, which entails that the inner lining is subjected to considerable load. The steep angle at which the clamping levers engage the inner lining also contributes to increase the load exerted onto the inner lining. Although the inner lining is very sturdy, it remains yielding to a certain extent in the clamping state. This leads to situations in which the clamping levers engaging the inner lining cannot be precisely controlled.
Starting from these premises, the object of the present invention is to modify the inner lining in such a manner that the clamping forces cannot exert such high deformations on the inner lining as is the case with the state of the art devices. The specific objective of the invention is to bring the clamping forces to arise on purpose and in a predictable manner and to act with short lever arms.
Starting from the adjusting device of the type mentioned above provided with a silent ratchet, the solution of this object is to provide the inner lining with a surroundings clamping groove having two lateral surrounding clamping surfaces, to design the clamping area as an engaging part adapted to said clamping groove, said engaging part having two sloping clamping sides, each cooperating with one clamping surface.
In a kinematic reversal, the inner lining is not provided with a clamping groove, a clamping ridge this time projects from the inner lining radially inward. In this embodiment, the solution of the object cited is that the inner lining is provided with a surrounding clamping ridge having two lateral surrounding clamping surfaces, that the clamping area is a covering part adapted to said clamping ridge, said covering part having two clamping flanks, each of them cooperating with a clamping surface.
With these adjusting devices, the clamping forces essentially act in axial direction and on very short paths. The curve described by the forces remains in the environment of the clamping groove or in the covering part. Substantially, the clamping forces merely subject the clamping groove to a load or, in the solution of kinematic reversal, it is the covering part which is subjected to load. But, with simple means, both parts may be made so sturdy mechanically that in the case of clamping only very slight deformations take place. These parts still remain lightweight since, as opposed to the state of the art, a considerable amount of material is being saved while stability is increased.
According to the invention, the curve of the clamping forces and the resulting reactions in the covering part or in the wall of the clamping groove is a relatively small closed revolution with a relatively short path. It is clearly located outside the axis. The paths of force are accordingly short. No sensible deformation of the inner lining has to be feared. The clamping forces compensate substantially on a short path, they are oriented toward each other.
The invention makes it possible to manufacture a silent ratchet that has good operational properties and an accurate response, that is lightweight and that also shows good properties in continuous operation.
As with the state of the art devices, it is advantageous to provide at least two pairs of clamping levers and to dispose said two pairs of clamping levers in mirror symmetry about a mirror plane running through the axis. In this way, two braking moments staggered by 180xc2x0 are preserved in case of clamping, which reduces the loads exerted on the axis of the silent ratchet.
It is furthermore advantageous to have the axis of the clamping lever arranged in the neighbourhood of an end area of the clamping lever. This results in an embodiment which is advantageous for controlling the releasing processes and allows to arrange the axis of the clamping lever in closer proximity to the inner lining than to the axis of the silent ratchet.
In another preferred embodiment a clamping spring is allocated to the at least one clamping lever, said clamping spring being disposed between the clamping lever and the second ratchet portion and biassing the clamping lever in a clamping position. As with the state of the art devices the silent ratchet is normally locked. In the pairs of clamping levers, those clamping levers undertake the locking function in one direction of rotation which are located in front in this direction of rotation. The clamping levers lying behind in the direction of rotation are trailed and, owing to the clamping spring, abut on the clamping groove or on the clamping ridge without any clamping function.
In still another development, the second ratchet portion is rotatably connected to a driven shaft, a release wheel being provided at the driving end which is capable of pivoting about the axis and which is provided with at least one dog projection which is located in the motion area of the clamping lever and of a dog flank of the second ratchet portion and which, on a pivotal movement of the release wheel leaving its normal position, presses the clamping lever, which is self-locking in the corresponding direction of rotation, out of the clamping position and retains it prior to contacting the dog flank. This construction permits to advantageously design the control of the clamping levers in a release position. Only short pivoting angles are required to press the clamping lever, which is locking in one direction of rotation, into the release position before the drive takes place in the pivoting direction considered.
In a particularly preferred embodiment, the distance between the axis of the clamping lever and the clamping area is at least 1.4 times greater, more specifically 1.6 to 2.5 times greater, preferably 1.8 times greater than the distance between the axis of the clamping lever and the inner lining. Contrary to the state of the art devices, the clamping levers engage the inner lining at an angle which is clearly farther away from a radial through the clamping point than it is the case with the state of the art devices. The angle made by a connecting line between the axis of the clamping lever and the clamping point on one side and by a radial through the axis of the clamping lever on the other side, is not inferior to 45xc2x0, it preferably is of approximately 60xc2x0. A secure clamping position and a good hold in the clamping point are hereby achieved, even when the parts effecting the clamping have been lubricated. The clamping point refers to the area of contact in which the actual clamping occurs between clamping area and clamping ridge or clamping groove.